Constant pressure pneumatic balancing tire inflation system

ABSTRACT

A constant pressure vehicle tire inflation system includes an air supply source. A first wheel valve is in fluid communication with a first tire of the vehicle, and a second wheel valve is in fluid communication with a second tire of the vehicle. A pneumatic conduit extends between and is in fluid communication with the air supply source and the wheel valves. At least a portion of the pneumatic conduit remains charged with air from at least one of the supply source and the tires. The system includes means for distributing air flow between the pneumatic conduit and the first and second wheel valves, in which the wheel valves and the means selectively maintain fluid communication between the first and second tires and the pneumatic conduit to provide pneumatic balancing between the tires, and the wheel valves provide emergency protection when a tire experiences significant pressure loss.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/194,617, filed on Jul. 29, 2011, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/369,163, filed on Jul. 30,2010.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to the art of tire inflation systems. Moreparticularly, the invention relates to tire inflation systems forheavy-duty vehicles such as trucks and tractor-trailers orsemi-trailers, which can operate as the vehicle is moving. Still moreparticularly, the invention is directed to a tire inflation system thatis a constant pressure system which continuously balances pneumaticpressure across all of the tires in the system, and provides emergencyprotection in the event a tire in the system experiences significantpressure loss.

2. Background Art

Heavy-duty vehicles typically include trucks and tractor-trailers orsemi-trailers. Tractor-trailers and semi-trailers, which shallcollectively be referred to as tractor-trailers for the purpose ofconvenience, include at least one trailer, and sometimes two or threetrailers, all of which are pulled by a single tractor. All heavy-dutyvehicles that are trucks or tractor-trailers include multiple tires,each of which is inflated with a fluid or gas, such as air, to anoptimum or recommended pressure. This optimum or recommended tirepressure typically is referred to in the art as the target inflationpressure or the target pressure.

However, it is well known that air may leak from a tire, usually in agradual manner, but sometimes rapidly if there is a problem with thetire, such as a defect or a puncture caused by a road hazard. As aresult, it is necessary to regularly check the air pressure in each tireto ensure that the tires are not significantly below the target pressureand thus under-inflated. Should an air check show that a tire isunder-inflated, it is desirable to enable air to flow into the tire toreturn it to the target pressure. Likewise, it is well known that theair pressure in a tire may increase due to increases in ambient airtemperature, so that it is also necessary to regularly check the airpressure in each tire to ensure that the tires are not greatly above thetarget pressure and thus over-inflated. Should an air check show that atire is over-inflated, it is desirable to enable air to flow out of thetire to return it to the target pressure.

The large number of tires on any given heavy-duty vehicle setup makes itimpractical to manually check and maintain the target pressure for eachand every tire. This difficulty is compounded by the fact that trailersof tractor-trailers or trucks in a fleet may be located at a site for anextended period of time, during which the tire pressure might not bechecked. Any one of these trailers or trucks might be placed intoservice at a moment's notice, leading to the possibility of operationwith under-inflated or over-inflated tires. Such operation may increasethe chance of less-than-optimum performance and/or reduced life of atire in service as compared to operation with tires at the targetpressure, or within an optimum range of the target pressure.

Moreover, should a tire encounter a condition as the vehicle travelsover-the-road that causes the tire to become under-inflated, such asdeveloping a leak from striking a road hazard, the life and/orperformance of the tire may be significantly reduced if theunder-inflation continues unabated as the vehicle continues to travel.Likewise, should a tire encounter a condition that causes it to becomesignificantly over-inflated, such as increasing pressure from anincreased ambient air temperature, the life and/or performance of thetire may be significantly reduced if the over-inflation continuesunabated as the vehicle continues to travel. The potential forsignificantly reduced tire life typically increases in vehicles such astrucks or tractor-trailers that travel for long distances and/orextended periods of time under such less-than-optimum inflationconditions.

Such a need to maintain the target pressure in each tire, and theinconvenience to the vehicle operator having to manually check andmaintain a proper tire pressure that is at or near the target pressure,led to the development of prior art tire inflation systems. In theseprior art systems, an operator selects a target inflation pressure forthe vehicle tires. The system then monitors the pressure in each tireand attempts to maintain the air pressure in each tire at or near thetarget pressure by inflating the tire when the monitored pressure dropsbelow the target pressure. These prior art tire inflation systemsinflate the tires by providing air from the air supply of the vehicle tothe tires by using a variety of different components, arrangements,and/or methods. Certain prior art systems are also capable of deflation,and these systems deflate the tires when the monitored pressure risesabove the target pressure by venting air from the tires to atmosphere.

While being satisfactory for their intended functions, tire inflationsystems of the prior art may experience disadvantages in certainsituations. For example, a first disadvantage in the prior art is thatmany prior art tire inflation systems are not capable of deflation. As aresult, when the air pressure in a tire increases to a level that isgreatly above the target pressure, typically due to increases in ambientair temperature, these systems are unable to reduce the pressure in thetires. As a result, such prior art tire inflation systems may allow thetires to operate in a significantly over-inflated condition, whichundesirably decreases performance of the tires and in turn decreases thelife of the tires.

A second disadvantage occurs in prior art tire inflation systems thatare capable of deflation. More particularly, deflation-capable systemstypically are electronically controlled, employingelectronically-operated solenoid valves, electronic controllers, andother electronic components, which are expensive and are often complexto install and configure. In addition, these electrical componentsrequire the use of the electrical system of the vehicle, which may beunreliable or even non-functional at times, in turn rendering theoperation of the tire inflation system unreliable and potentiallynon-functional. As a result, prior art deflation-capable tire inflationsystems which are electronically controlled are often undesirablyexpensive, complex, and potentially undependable.

A third disadvantage is that most prior art tire inflation systems whichare capable of deflation, and particularly electronically-controlledsystems, are not constant-pressure systems and thus do not activelymonitor tire pressure. More particularly, in the prior art, theprincipal goal of most deflation-capable tire inflation systems has beento respond to operator-controlled adjustments of the target inflationpressure, rather than to actively monitor tire pressure and continuouslymaintain the target inflation pressure. As a result, in mostdeflation-capable prior art tire inflation systems, when the system isnot performing inflation or deflation, the pneumatic conduit of thesystem is exhausted to atmosphere.

In such a system, without air pressure in the pneumatic conduit,electronic controls are employed to periodically check tire pressure,and to in turn trigger or commence inflation or deflation, as may berequired. Because such prior art systems are capable of only providing aperiodic check of tire pressure, any inflation or deflation to bring thetires to the target pressure only takes place following the periodiccheck. This lack of ability of prior art systems to continuously monitortire pressure and dynamically respond to pressure changes undesirablyreduces the ability of the system to actively or quickly respond toreduced tire pressure conditions, such as in the case of an air leak,and to increased tire pressure conditions, such as an increase inambient temperature. Moreover, as mentioned above, the electroniccontrols employed by prior art tire inflation systems are expensive,complex, and require power from the electrical system of the vehicle,which may be unreliable.

A fourth disadvantage of prior art tire inflation systems is that mostsystems, and particularly those prior art systems which areconstant-pressure systems, do not provide balancing of pneumaticpressure across all of the tires in the system. More particularly, asdescribed above, a typical heavy-duty vehicle includes multiple tires,and each one of those tires is operatively and independently connectedto a single tire inflation system. More specifically, most prior arttire inflation systems are connected directly to each tire, and ofthese, many include a one-way check valve for each tire that preventsair from exiting the tire. In such a configuration, the tire inflationsystem monitors the pressure in each tire, inflating any tire that fallsbelow the target pressure. While such separate inflation of each tire issatisfactory for its intended purpose, such prior art systems are notcapable of deflation of the tires, and thus are unable to reduce thepressure in the tires when it increases to a level that is greatly abovethe target pressure.

In addition, such prior art systems lack fluid communication between thetires. Without fluid communication between the tires, different tiresmay be inflated to slightly different pressure levels, which isundesirable. More particularly, many heavy-duty vehicles include adual-wheel or dual-tire configuration, in which two tires are mounted ona single wheel end assembly. Because the two tires are mechanicallyconnected to each other through their respective mounting on the samewheel end assembly, they rotate at the same speed during vehicleoperation. Although both wheels are designed to be the same diameter,their actual respective diameters are slightly different, since the lackof fluid communication between them causes them to be inflated toslightly different pressure levels. The difference in actual respectivediameters between the tires, while they rotate at the same speed, causesone of the tires to experience dragging, which is also referred to inthe art as scrubbing. Scrubbing of a tire causes premature wear on thattire, and undesirably shortens the life of the tire.

In addition, the lack of fluid communication between the tiresundesirably increases the chance that a tire may operate with anexcessively low inflation pressure. For example, in the event that onetire in the system is about fifty percent (50%) below the targetinflation pressure, a prior art system may take a significant amount oftime to bring the pressure in the low tire up to the target pressure.During that time, it is possible for the tire to be operated in asignificantly under-inflated state, which decreases its life. Incontrast, when there is fluid communication between the tires, each ofthe remaining tires in the system passes air to the tire that is belowthe target inflation pressure. Because multiple tires, such as seven ormore tires, each pass a relatively small amount of air to thelow-pressure tire, the low pressure tire receives air much more quickly,and all of the tires in the system balance at a pressure that is onlyslightly below the target pressure, such as about five percent (5%)below the target pressure. In the art, it is more desirable to operatethe vehicle with multiple tires that are slightly below the targetpressure until the system is able to bring them up to the targetpressure, rather than operating the vehicle with a single tire that issignificantly below the target pressure.

A fifth disadvantage of prior art tire inflation systems occurs in thefew prior art systems which do provide balancing of pneumatic pressureacross all of the tires. More specifically, in prior art tire inflationsystems that do provide balancing of pneumatic pressure, all of thetires are in fluid communication with one another, and the tires thushave a generally uniform, or balanced, inflation pressure. However,these systems do not provide emergency protection of the tires in theevent that one tire experiences a significant pressure loss. Forexample, if a specific tire is punctured or a pneumatic conduit at thetire ruptures, it is important to pneumatically isolate the system fromthat tire due to the fluid communication between the tires. In such asystem, if the system is not isolated from a tire that is experiencing asignificant pressure loss, the uniform inflation pressure of all of thetires may decrease significantly, which may place an excessive inflationdemand on the system. The system may not be able to meet this demand,which may result in the tires being operated below the target inflationpressure, in turn reducing tire life, and/or the system may actuateexcessively to attempt to meet the demand, thereby reducing the life ofthe system.

As a result, there is a need in the art for a tire inflation system thatovercomes the disadvantages of the prior art by providing aconstant-pressure tire inflation system that is capable of deflation, isnot electronically controlled, balances pneumatic pressure across all ofthe tires in the system, and includes emergency protection of the tiresin the event that one or more tires experiences a significant pressureloss. The constant pressure pneumatic balancing tire inflation system ofthe present invention satisfies this need, as will be described indetail below.

BRIEF SUMMARY OF THE INVENTION

An objective of the present invention is to provide a tire inflationsystem that is a constant-pressure tire inflation system that is capableof deflation.

Another objective of the present invention is to provide a tireinflation system that does not employ electronic components for control.

Yet another objective of the present invention is to provide a tireinflation system that enables balancing of pneumatic pressure across allof the tires in the system.

Still another objective of the present invention is to provide a tireinflation system that includes emergency protection of the tires in theevent that one or more tires experiences a significant pressure loss.

These objectives and others are obtained by the constant pressurepneumatic balancing tire inflation system of the present invention. Byway of example, a constant pressure vehicle tire inflation systemincludes an air supply source. A first wheel valve is in fluidcommunication with a first tire of the vehicle, and a second wheel valveis in fluid communication with a second tire of the vehicle. A pneumaticconduit extends between and is in fluid communication with the airsupply source and the wheel valves. At least a portion of the pneumaticconduit remains charged with air from at least one of the supply sourceand the tires. The system includes means for distributing air flowbetween the pneumatic conduit and the first and second wheel valves, inwhich the wheel valves and the means selectively maintain fluidcommunication between the first and second tires and the pneumaticconduit to provide pneumatic balancing between the tires.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The preferred embodiments of the present invention, illustrative of thebest mode in which Applicants have contemplated applying the principles,are set forth in the following description and are shown in thedrawings, and are particularly and distinctly pointed out and set forthin the appended claims.

FIG. 1 is a fragmentary cross-sectional perspective view of a portion ofan axle spindle and a wheel end assembly, having certain components of atire inflation system of the prior art mounted thereon, and a brake drumand tire rims mounted on the hub of the wheel end assembly;

FIG. 2 is a fragmentary cross-sectional elevational view of componentsof a first exemplary embodiment constant pressure pneumatic balancingtire inflation system of the present invention, shown incorporated intoan axle spindle;

FIG. 3A is the view of first exemplary embodiment constant pressurepneumatic balancing tire inflation system shown in FIG. 2, withpneumatic flow arrows added to indicate an inflation mode;

FIG. 3B is the view of first exemplary embodiment constant pressurepneumatic balancing tire inflation system shown in FIG. 2, withpneumatic flow arrows added to indicate a deflation mode;

FIG. 4 is an outboard perspective view of the hub cap and dual wheelvalve of the first exemplary embodiment constant pressure pneumaticbalancing tire inflation system of the present invention shown in FIG.2;

FIG. 5 is a fragmentary cross-sectional elevational view of componentsof the first exemplary embodiment constant pressure pneumatic balancingtire inflation system, shown in an inflation-only configuration;

FIG. 6 is a fragmentary cross-sectional elevational view of componentsof the first exemplary embodiment constant pressure pneumatic balancingtire inflation system, shown in a balancing-only configuration;

FIG. 7 is a perspective view, with portions broken away and in section,of certain components of a second exemplary embodiment constant pressurepneumatic balancing tire inflation system of the present invention;

FIG. 8 is an inboard elevational view of components of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 7, with hiddenportions represented by dashed lines;

FIG. 9 is a cross-sectional elevational view of components of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 7;

FIG. 10 is an exploded perspective view of the components of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 7;

FIG. 11A is an outboard perspective view of the hub cap of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 7;

FIG. 11B is an inboard perspective view of the hub cap of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 7;

FIG. 12A is an inboard perspective view of the pneumatic distributionplate of the second exemplary embodiment constant pressure pneumaticbalancing tire inflation system of the present invention shown in FIG.7;

FIG. 12B is an outboard perspective view of the pneumatic distributionplate of the second exemplary embodiment constant pressure pneumaticbalancing tire inflation system of the present invention shown in FIG.7;

FIG. 13 is an inboard elevational view of components of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention, shown in an inflation-onlyconfiguration, with hidden portions represented by dashed lines;

FIG. 14 is a cross-sectional elevational view of components of thesecond exemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 13;

FIG. 15 is an inboard elevational view of components of the secondexemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention, shown in a balancing-onlyconfiguration, with hidden portions represented by dashed lines;

FIG. 16 is a cross-sectional elevational view of components of thesecond exemplary embodiment constant pressure pneumatic balancing tireinflation system of the present invention shown in FIG. 15;

FIG. 17 is a fragmentary cross-sectional elevational view of componentsof a third exemplary embodiment constant pressure pneumatic balancingtire inflation system of the present invention, shown incorporated intoan axle spindle; and

FIG. 18 is a fragmentary elevational view, partially in section, of anoptional hose fitting system for use with and shown mounted on aconstant pressure pneumatic balancing tire inflation system of thepresent invention.

Similar numerals refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

In order to better understand the constant pressure pneumatic balancingtire inflation system of the present invention and the environment inwhich it operates, the components of an exemplary prior art tireinflation system, and the vehicle structures upon which they are mountedare shown in FIG. 1, and now will be described.

One or more axles 10 typically depend from and extend transverselyacross a heavy-duty vehicle (not shown). Each axle 10 has two ends, witha wheel end assembly 12 mounted on each one of the ends. For thepurposes of convenience and clarity, only one end of axle 10 and itsrespective wheel end assembly 12 will be described herein. In addition,axle 10 is shown by way of example in FIG. 1 as a non-drive axle, withthe understanding that the present invention applies to all types ofaxles known in the art, including drive axles and non-drive axles.Moreover, heavy-duty vehicles include trucks and tractor-trailers orsemi-trailers, and the tractor-trailers or semi-trailers typically areequipped with one or more trailers. Reference herein shall be madegenerally to a heavy-duty vehicle for the purpose of convenience, withthe understanding that such reference includes trucks, tractor-trailersand semi-trailers, and trailers thereof.

Axle 10 includes a central tube (not shown), and an axle spindle 14 isintegrally connected, by any suitable means such as welding, to each endof the central tube. Wheel end assembly 12 includes a bearing assemblyhaving an inboard bearing 16 and an outboard bearing 18 immovablymounted on the outboard end of axle spindle 14. A spindle nut assembly20 threadably engages the outboard end of axle spindle 14 and securesbearings 16, 18 in place. A wheel hub 22 is rotatably mounted on inboardand outboard bearings 16, 18 in a manner well known to those skilled inthe art.

A hub cap 24 is mounted on the outboard end of hub 22 by a plurality ofbolts 26, each one of which passes through a respective one of aplurality of openings 28 formed in the hub cap, and threadably engages arespective one of a plurality of aligned threaded openings 30 forming inthe hub. In this manner, hub cap 24 closes the outboard end of wheel endassembly 12. A main continuous seal 32 is rotatably mounted on theinboard end of wheel end assembly 12 and closes the inboard end of theassembly. In a typical heavy-duty vehicle dual-wheel configuration, aplurality of threaded bolts 34 are used to mount a brake drum 36 and apair of tire rims 38 on wheel end assembly 12. Each one of a pair oftires (not shown) is mounted on a respective one of tire rims 38, asknown in the art.

A prior art tire inflation system is indicated generally at 40. Acentral bore 48 is formed in axle 10, through which a pneumatic conduit44 of tire inflation system 40 extends toward an outboard end of axlespindle 14. Pneumatic conduit 44 is fluidly connected to and extendsbetween the vehicle air supply, such as an air tank (not shown), and arotary union 42. Rotary union 42 is attached to a plug 50 that ispress-fit in a machined counterbore 52 formed in axle central bore 48 atan outboard end of axle spindle 14, and as known in the art, facilitatesthe connection of static pneumatic conduit 44 to an air tube assembly46, which rotates with the tire.

Air tube assembly 46 includes a first tube 54 that is fluidly connectedat one of its ends to rotary union 42 inside hub cap 24, and is fluidlyconnected at the other of its ends to a tee fitting 56, which passesthrough the hub cap and is secured to the hub cap. Additional air tubes(not shown) are fluidly connected to and extend from each one of twooutlets of tee fitting 56 outside of hub cap 24 to each one of arespective pair of tires mounted on rims 38. In this manner, air passesfrom the vehicle air tank, through pneumatic conduit 44, rotary union42, first air tube 54, hub cap 24 and tee fitting 56, and to the tires.

Prior art tire inflation system 40, while being satisfactory for itsintended function, includes certain disadvantages. For example, manyprior art tire inflation systems 40 are not capable of deflation, andmay thus allow the tires to operate in a significantly over-inflatedcondition, which undesirably decreases performance of the tires and inturn decreases the life of the tires. In addition, in those prior arttire inflation systems 40 that are capable of deflation, electroniccontrol is often used, employing undesirably expensive and complexelectronically-operated components, which may also be unreliable due todependence on the electrical system of the vehicle. Moreover, many priorart tire inflation systems 40 that are capable of deflation are notconstant-pressure systems, thereby again requiring undesirablyexpensive, complex and potentially unreliable electronically-operatedcomponents, and lack the ability to continuously monitor tire pressureand quickly respond to pressure changes.

In addition, most prior art tire inflation systems 40 do not providebalancing of pneumatic pressure across all of the tires in the system,which prevents deflation of the tires, and which may allow the tires toundesirably operate in a significantly over-inflated condition. Inaddition, a lack of balancing of pneumatic pressure prevents fluidcommunication between the tires, which may lead to scrubbing andpremature wear of a tire in a dual-wheel configuration, and alsoundesirably increases the chance that a tire may operate with anexcessively low inflation pressure. In those prior art tire inflationsystems 40 that do provide balancing of pneumatic pressure across all ofthe tires, there is no emergency protection provided for the tires inthe event that one or more tires experiences a significant pressureloss, which may place an excessive inflation demand on the system,resulting in the tires being operated below the target inflationpressure and thus reducing tire life, and/or the life of the system maybe reduced by actuating excessively in an attempt to compensate for thepressure loss. The constant pressure pneumatic balancing tire inflationsystem of the present invention overcomes these disadvantages, as willnow be described.

The present invention is directed to a tire inflation system that is apneumatically-controlled, constant-pressure system which is capable ofdeflation, continuously balances pneumatic pressure across all of thetires in the system, and provides emergency protection in the event atire in the system experiences significant pressure loss. Specificinventive components are employed to achieve a constant pressure,continuously balancing system. These components preferably include: ahub cap that acts as a manifold, in which the hub cap includes a modularconstruction; a wheel valve that is integrated into the hub cap, inwhich the wheel valve includes a certain construction for control of adual-wheel configuration of a heavy-duty vehicle, and that enables thewheel valve to be mounted on the outside of the hub cap, inside the hubcap, or integrated into the outboard wall of the hub cap; and anoptional non-axial tire hose fitting for the system.

It is to be understood that reference herein to a constant pressure tireinflation system includes all tire inflation systems with regulatedpressure. For example, constant pressure systems include systems inwhich all or a significant portion of the pneumatic conduit of thesystem remains pressurized or charged with compressed air when thesystem is not engaged in inflation or deflation, and systems in whichsuch pressurization of the pneumatic conduit may be interrupted by aswitch or other component.

Turning now to FIGS. 2-4, a first exemplary embodiment of a constantpressure pneumatic balancing tire inflation system of the presentinvention is indicated generally at 70. It is to be understood that tireinflation system 70 includes an air source, such as an air tank (notshown), which is in fluid communication with the vehicle tires (notshown) via a pneumatic conduit 96 and other components, which will bedescribed in detail below. It is also to be understood that means knownto those skilled in the art, such as mechanically-operated regulatorvalves (not shown), are fluidly connected to pneumatic conduit 96 andare employed to monitor the pneumatic pressure in the tires and toactuate inflation and/or deflation of the tires.

First exemplary embodiment tire inflation system 70 includes a hub cap72, which in turn includes a cylindrical side wall 74, and an outboardwall 76 integrally formed with the outboard end of the side wall andextending generally perpendicular to the side wall. It is to beunderstood that other shapes and configurations of hub cap side wall 74and outboard wall 76 may be employed without affecting the overallconcept or operation of the present invention, such as an integrateddome or cone shape formed as one piece or multiple pieces. Aradially-extending flange 78 is formed on the inboard end of side wall74, and is formed with a plurality of bolt openings (not shown) toenable bolts to secure hub cap 72 to the outboard end of wheel hub 22(FIG. 1). In this manner, hub cap 72 defines an interior compartment 80.It is to be understood that means known to those skilled in the artother than bolts may be used to secure hub cap 72 to wheel hub 22, suchas a threaded connection between the hub cap and wheel hub, other typesof mechanical fasteners, and/or a press fit.

Hub cap outboard wall 76 includes an inboard surface 82. Bolts (notshown) or other fastening means, including mechanical fasteners andjoining techniques, such as welding, adhesives, and the like, are usedto secure a cylindrical housing 84 of a rotary union 86 to a recess 136formed in inboard surface 82 of hub cap outboard wall 76. A gasket 88 isdisposed between rotary union housing 84 and inboard surface 82 of hubcap outboard wall 76 to provide a seal between the rotary union housingand the inboard surface of the hub cap outboard wall. Rotary union 86further includes a stem 90, which in turn includes a threaded inboardportion 92 that engages a female hose connector 94 of tire inflationsystem pneumatic conduit 96 by any threaded or non-threaded knownpneumatic connection means, including threads, push-to-connect fittings,tube fittings, crimped fittings, friction fittings, hose clamps, and thelike. Rotary union stem 90 further includes an outboard portion 98 thatis rotatably mounted in rotary union housing 84.

To facilitate the rotatable mounting of outboard portion 98 of stem 90in rotary union housing 84, each one of a pair of bearings 102 ispressed onto the rotary union stem outboard portion, and the outboardportion of the stem, with the bearings, is pressed into a mountingcavity 104 formed in rotary union housing 84. Bearings 102 thus enablehub cap 72 and rotary union housing 84 to rotate about rotary union stem90, which remains static. To provide an additional seal between rotaryunion stem outboard portion 98 and rotary union housing 84, an outboardgroove 106 is formed in the housing, and a rotary seal 108 is disposedin the groove on the outboard end of rotary union stem 90. Rotary unionstem 90 is formed with a central bore 100, which facilitates the passageof air through rotary union 86. Because tire inflation system pneumaticconduit 96 is fluidly connected to an air supply of the vehicle (notshown), air flows from the vehicle air supply, through pneumatic conduit96, through central bore 100 of rotary union stem 90, and into a supplycavity 110 formed in hub cap outboard wall 76, as indicated by arrow A1(FIG. 3A).

Supply cavity 110 is formed in axial alignment with an axial centerlineC of axle 12 and wheel end assembly 12 (FIG. 2). A center port 140formed in hub cap outboard wall 76 is in fluid communication with andextends longitudinally along axial centerline C from supply cavity 110to an outboard surface 142 of the hub cap outboard wall. A wheel valveassembly 144, shown by way of example as a dual wheel valve, is attachedto the outboard surface 142 of hub cap outboard wall 76, and is in fluidcommunication with center port 140, as will be described in greaterdetail below. The attachment of dual wheel valve 144 to outboard surface142 of outboard wall 76 is provided by bolts 146 (FIG. 4 or otherfastening means, including mechanical fasteners and joining techniques,such as welding, adhesives, press fit and the like. Preferably, a gasketor O-ring 138 is disposed between dual wheel valve 144 and outboardsurface 142 of outboard wall 76 about center port 140 to provide a fluidcommunication seal between the dual wheel valve and the hub cap outboardwall.

Dual wheel valve 144 incorporates two separate wheel valves 148A, 148Bin a single body 150. Dual wheel valve 144 enables air to be provided totwo separate tires from a single port, that is, center port 140 in hubcap 72, with a wheel valve 148A, 148B for each respective tire, withoutemploying exterior pneumatic conduit or hoses. More particularly, airflows through center port 140 and into a distribution plate 152 of valvebody 150. Distribution plate 152 divides the air flow into two separatepaths, as shown by arrows A2 (FIG. 3A), so that air flows into eachwheel valve 148A, 148B.

Each wheel valve 148A, 148B preferably is a diaphragm valve that remainsopen during all normal operating conditions, and is also capable ofisolating each tire in tire inflation system 70 from one or more tiresthat experience a significant pressure loss, such as if a tire ispunctured. Each wheel valve 148A, 148B is also capable of isolating eachtire from other components of tire inflation system 70 if the systemdevelops a leak that exceeds the inflation capacity of the system. Moreparticularly, each wheel valve 148A, 148B preferably is spring biasedand actuates or opens at a selected pressure setting or pressure level,which is reasonably below or less than the minimum pressure that wouldbe expected to be utilized as a target tire pressure.

For example, wheel valve 148A, 148B may open or actuate at a reasonablepredetermined pressure level that is lower than the target inflationpressure, such as at about 70 pounds per square inch (psi) when thetarget inflation pressure is at about 90 psi. Alternatively, wheel valve148A, 148B may open or actuate at a pressure level that is a setreasonable amount less than the target inflation pressure, such as avalue of about 20% less than the target inflation pressure, or a valueof about 20-30 psi less than the target inflation pressure. In thismanner, each wheel valve 148A, 148B remains open during all normaloperating conditions, thereby enabling air to flow to the tires, andalso enabling fluid communication between the tires for balancing ofpneumatic pressure, as will be described in greater detail below.

In the event of a significant pressure loss in one of the tires or inthe pneumatic components of tire inflation system 70 that allows thepressure level in pneumatic conduit 96 to fall below the selectedpressure setting, the spring bias of wheel valves 148A, 148B causes themto close, thus isolating each tire from the rest of the tire inflationsystem. For example, if the opening or actuation pressure level of wheelvalve 148A, 148B is 70 psi and the pressure in pneumatic conduit 96drops below 70 psi, each wheel valve closes and thus isolates the tires.Actuation of each wheel valve 148A, 148B at a reasonable pressure levelbelow the target inflation pressure prevents excessive deflation of thetires and thereby provides emergency protection, in contrast to wheelvalves of the prior art. More particularly, prior art wheel valves openat an extremely low pressure level, such as about 10-20 psi. As aresult, in the event that one or more tires experience a significantpressure loss or system 70 develops a leak that exceeds the inflationcapacity of the system, the prior art wheel valves remain open until thesystem pressure drops to 10-20 psi, which in turn allows significantundesirable deflation of the tires.

Each wheel valve 148A, 148B also provides means to enable reduction ofthe pressure loss in the tires when the vehicle has been parked byresponding to the engagement of the vehicle parking brake, or to otherconditions that indicate the vehicle has been parked. More particularly,when a vehicle has been parked for an extended period of time, thepneumatic pressure in the vehicle supply tank may drop or bleed down dueto small air leaks that are typical in any pneumatic system. If theinflation path from the supply tank to the tires remains open, thepneumatic pressure in the tires drops when the pneumatic pressure in thesupply tank drops. This may be a drop of up to about twenty-five (25)psi for each tire. Then, when the vehicle is started up to prepare forover-the-road travel, the tires 14 must be re-inflated up to or near thetarget pressure, which may involve adding about 25 psi to multipletires. Such re-inflation typically takes a great deal of time, and ifthe vehicle operator does not wait for the tires to be re-inflated tothe target pressure before operating the vehicle, the tires in turn maybe operated in an under-inflated condition until the target pressure isreached, which reduces the life of the tires. To minimize pressure lossand the need to provide significant re-inflation of the tires, eachwheel valve 148A, 148B can be rapidly and/or reliably closed when thevehicle is parked, thus enabling isolation of the tires from the supplytank, as more fully described in a separate Application entitled “TireInflation System with Discrete Deflation Circuit” being filedconcurrently herewith, and which is assigned to the same Assignee as thepresent invention.

When each wheel valve 148A, 148B is open, air flows from each respectivewheel valve through a respective offset port 154A, 154B, as indicated byarrows A3 (FIG. 3A). Each offset port 154A, 154B is formed in hub capoutboard wall 76 in an axial orientation and located radially outward ofcenter port 140 in alignment with and in fluid communication with a portof its respective wheel valve 148A, 148B. Each offset port 154A, 154Bextends from outboard surface 142 of hub cap outboard wall 76 to and influid communication with a respective cylindrical bore 112A, 112B, whichis also formed in the hub cap outboard wall. Preferably, a gasket orO-ring 156A, 156B is disposed between dual wheel valve 144 and outboardsurface 142 of hub cap outboard wall 76 about each respective offsetport 154A, 154B to provide a fluid communication seal between the dualwheel valve and the hub cap outboard wall.

With continuing reference to FIGS. 2-4, cylindrical bores 112A, 112B areformed in hub cap outboard wall 76 to enable the connection of tirehoses 118A, 118B to hub cap 72. Preferably, cylindrical bores 112A, 112Bare formed approximately one-hundred-eighty (180) degrees from oneanother in hub cap outboard wall 76, which enables optimum configurationfor two tires hoses 118A, 118B, with each hose extending to a respectiveone of a pair of tires of a heavy-duty vehicle dual-wheel configuration,as will be described in greater detail below. Each bore 112A, 112Bextends radially inwardly from the exterior of hub cap cylindrical sidewall 74 and generally perpendicular to its respective offset port 154A,154B, and is in fluid communication with its respective offset port.

Reference shall now be made to a first bore 112A and its relatedstructure, components and configuration for the purpose of convenience,with the understanding that such structure, components and configurationalso applies to second bore 112B. Hub cap outboard wall 76 preferably isformed with features such as threads 116 about each bore 112A, whichthreadably engage a coupling 114 of tire hose 118A to secure the directconnection of the tire hose to the hub cap. Each tire hose 118A alsoincludes a tire hose fitting 120 and a first check valve assembly 134,which preferably is a Schrader-type or stem-type check valve. Tire hosefitting 120 is received in a fixed bushing or sleeve 122 that seats inbore 112A, and Schrader valve 134 seats in the tire hose fitting. Whentire hose 118A is connected to hub cap 72, Schrader valve 134 is heldopen by a poppet valve assembly 124, which is described in detail below,to enable air to flow through the Schrader valve. When tire hosecoupling 114 and fitting 120 are uncoupled and removed from sleeve 122,Schrader valve 134 remains with the hose coupling to prevent excessiveescape of air from the tire upon removal of tire hose 118A, and thesleeve remains in the bore.

A second check valve assembly 124, which preferably is a poppet valve,seats in sleeve 122 and prevents excessive venting of air from tireinflation system 70 upon the removal of tire hose 118A from hub cap 72.More particularly, sleeve 122 is formed with a taper 126 on its radiallyinward end, which corresponds to the radially inward end of bore 112.Poppet valve assembly 124 includes a spring 128, a seat 130, and ano-ring 132 mounted on the seat. When tire hose 118A is connected to hubcap 72, tire hose fitting 120 pushes seat 130, o-ring 132 and spring 128radially inwardly, which creates a space or gap between the o-ring andsleeve taper 126 through which air flows. When tire hose 118A is removedfrom hub cap 72, the bias of spring 128 urges seat 130 and o-ring 132radially outwardly, so that the o-ring contacts sleeve taper 126 toclose the space or gap, thereby preventing air from flowing throughpoppet valve assembly 124.

The structure of first embodiment tire inflation system 70 providescontinuous balancing of pneumatic pressure across all of the tires inthe system. More particularly, in a pneumatically balanced system 70,the tires are in fluid communication with one another, and according tothe principles of fluid flow, all of the tires have a generally uniform,or balanced, inflation pressure. When this uniform inflation pressure isabove the target pressure, the means that are employed to monitor thetire pressure enable tire inflation system 70 to decrease the uniformpressure by venting excess air to atmosphere as described above, whichin turn respectively decreases the inflation pressure of all of thetires in the system to the target pressure. When this uniform inflationpressure is below the target pressure, the means that are employed tomonitor the tire pressure enable tire inflation system 70 to increasethe uniform pressure by supplying air from a vehicle air tank asdescribed above, which in turn respectively increases the inflationpressure of all of the tires in the system to the target pressure.

In addition, such fluid communication between all of the tires in tireinflation system 70 enables each pair of tires in a dual-wheelconfiguration to have the same pressure level and thus the same actualdiameter, which reduces or eliminates the chance that one of the tireswill experience scrubbing, which increases the life of the tires.Moreover, the fluid communication between all of the tires in tireinflation system 70 enables tires that are at the target pressure tocontribute air to a tire with an excessively low inflation pressure,reducing the chance that a tire may operate with an excessively lowinflation pressure.

With particular reference now to FIGS. 3A and 3B, the continuousbalancing of pneumatic pressure of first embodiment tire inflationsystem 70 is provided by the unique manifolding path provided by hub cap72 and dual wheel valve 144, which is integrated or directly attached tothe hub cap. More particularly, the manifolding path may be illustratedusing inflation of the vehicle tires by way of example.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure in the tiresis below a desired level, the means actuate inflation of the tires.During inflation, as shown in FIG. 3A, air flows from the vehicle supplytank, through pneumatic conduit 96, through central bore 100 of rotaryunion stem 90 and into supply cavity 110, as indicated by arrow A1. Airthen flows from supply cavity 110 into center port 140 and enters dualwheel valve 144, where the air flow is split into two paths or flows bydistribution plate 152, as indicated by arrows A2. Air then flowsthrough each respective wheel valve 148A, 148B and into each respectiveoffset port 154A, 154B, as indicated by arrows A3. Air flows from eachrespective offset port 154A, 154B through a respective poppet valveassembly 124 and check valve assembly 120 in corresponding bore 112A,112B, as indicated by arrows A4, and into tire hoses 118A, 118B andrespective tires. Under normal operating conditions, this manifoldingair path remains open in first embodiment tire inflation system 70 toprovide a constant-pressure system that continuously balances pneumaticpressure across all of the tires in the system during inflation.

More particularly, first tire hose 118A, first cylindrical bore 112A,first offset port 154A, and first wheel valve 148A fluidly communicatewith second wheel valve 148B, second offset port 154B, secondcylindrical bore 112B, and second tire hose 118B at center port 140along the fluid path provided from each respective wheel valve to thecenter port by distribution plate 152. This fluid path provides fluidcommunication between each tire in a dual-wheel configuration. Inaddition, as indicated by arrow A1, the fluid path continues from centerport 140 through supply cavity 110, central bore 100 of rotary unionstem 90, and through pneumatic conduit 96. Pneumatic conduit 96 isfluidly connected to the remainder of the tires in the system, and thusenables fluid communication between all of the tires in tire inflationsystem 70. Such fluid communication between the tires enables them tohave a generally uniform, or balanced, inflation pressure.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure in the tiresis above a desired level, the means actuate deflation of the tires.Typically in deflation, air is removed from the system via pneumaticconduit 96 and vented to atmosphere. The manifolding air path remainsopen in first embodiment tire inflation system 70 during deflation, asshown in FIG. 3B. More specifically, when each tire hose 118A, 118B isconnected to hub cap 72, tire hose fitting 120 in each respectivecylindrical bore 112A, 112B maintains each respective poppet valveassembly 124 in an open position, thereby enabling air to flow out ofthe tires through check valve assembly 134 and the poppet valveassembly, as indicated by arrows B1. Air then flows through eachrespective offset port 154A, 154B to each respective wheel valve 148A,148B, as indicated by arrows B2.

More particularly, as described above, each wheel valve 148A, 148Bpreferably is spring biased and actuates or opens at a selected pressurelevel, such as about 70 psi, which is below the minimum pressure thatwould be expected to be utilized as a target tire pressure. As long asthe pressure in the pneumatic conduit 96 is above this selected pressurelevel, each wheel valve 148A, 148B remains open, thereby enabling air toflow through each wheel valve. Air then flows from each respective wheelvalve 148A, 148B through distribution plate 152, as indicated by arrowsB3. After flowing through distribution plate 152, each separate air flowstream merges into a single air flow stream in hub cap center port 140.

It is at this point that fluid communication between the tires forcontinuous balancing of pneumatic pressure takes place. Moreparticularly, first tire hose 118A, first cylindrical bore 112A, firstoffset port 154A, and first wheel valve 148A fluidly communicate withsecond wheel valve 148B, second offset port 154B, second cylindricalbore 112B, and second tire hose 118B at center port 140 along the fluidpath provided from each respective wheel valve to the center port bydistribution plate 152. This fluid path provides fluid communicationbetween each tire in a dual-wheel configuration. In addition, asindicated by arrow B4, the fluid path continues from center port 140through supply cavity 110, central bore 100 of rotary union stem 90, andthrough pneumatic conduit 96. Pneumatic conduit 96 is fluidly connectedto the remainder of the tires in the system, and thus enables fluidcommunication between all of the tires in tire inflation system 70. Suchfluid communication between the tires enables them to have a generallyuniform, or balanced, pressure when system 70 is in a deflation mode.

It is to be understood that the manifolding air path described above forfirst embodiment tire inflation system 70 provides fluid communicationbetween all of the tires in the system during inflation and deflation,and when the system is not engaged in inflation or deflation. As aresult, first embodiment tire inflation system 70 provides aconstant-pressure system that continuously balances pneumatic pressureacross all of the tires in the system.

In this manner, hub cap 72 and integrated dual wheel valve 144 of firstembodiment tire inflation system 70 cooperate to provide a uniquemanifolding path that continuously balances pneumatic pressure betweenall of the tires in tire inflation system 70 under normal operatingconditions, without any electronic components or controllers. Inaddition, first embodiment tire inflation system 70 compensates forambient temperature changes, as the fluid communication between thetires provided by hub cap 72 and integrated dual wheel valve 144 enablesincreases in pneumatic pressure that are attributable to increases inambient temperature to be relieved to atmosphere through a control valveassembly (not shown), which is fluidly connected to pneumatic conduit96. The fluid communication between the tires provided by hub cap 72 andintegrated dual wheel valve 144 also enables decreases in pneumaticpressure that are attributable to decreases in ambient temperature to beaddressed through the introduction of air into pneumatic conduit 96, asdescribed above.

Moreover, the unique manifolding path provided by hub cap 72 andintegrated dual wheel valve 144 connects rotary union 86, the dual wheelvalve, and tire hoses 118A, 118B with no intermediate hoses or conduit.The elimination of intermediate hoses or conduit in turn reduces thecost and complexity of first embodiment tire inflation system 70 whencompared to prior art tire inflation systems 40.

Integrated dual wheel valve 144 of first embodiment tire inflationsystem 70 also provides emergency protection in the event that a tire inthe system experiences significant pressure loss, or if the componentsof the system develop a leak that exceeds the inflation capacity of thesystem. For example, if a specific tire is punctured or a pneumaticconduit ruptures, the pressure in pneumatic conduit 96 may drop. Whenthe pneumatic pressure in pneumatic conduit 96 drops, wheel valves 148A,148B detect the pressure drop. As described above, when the pressuredetected by wheel valves 148A, 148B drops below the selected actuationor opening pressure level for the valves, which is below the minimumpressure that would be expected to be utilized as a target tirepressure, the valves close. Once wheel valves 148A, 148B close, air flowto and from respective tire hoses 118A, 118B and thus the respectivetires is terminated, thereby isolating each tire from the remainder oftire inflation system 70.

Each wheel valve 148A, 148B also provides means to reduce the pressureloss in the tires when the vehicle has been parked for an extendedperiod of time. More particularly, each wheel valve 148A, 148B is ableto be rapidly and/or reliably closed when the vehicle is parked, therebyenabling isolation of the tires from the supply tank.

Dual wheel valve 144 of first embodiment tire inflation system 70includes additional advantages. For example, by incorporating twoseparate wheel valves 148A, 148B into a single valve body 150, dualwheel valve 144 is able to supply air to multiple tires from a singlepneumatic supply conduit 96, and in cooperation with hub cap 72, is ableto balance air between those tires. Dual wheel valve 144 provides aconvenient, compact unit, while also monitoring the pneumatic pressurein separate tires via separate wheel valves 148A, 148B. By being mounteddirectly to hub cap 72, dual wheel valve 144 eliminates external hosesor conduit, in turn reducing the cost and complexity of first embodimenttire inflation system 70 when compared to prior art tire inflationsystems 40. In addition, by being a discrete unit, dual wheel valve 144may be built or constructed separately from hub cap 72 and later mountedon the hub cap, thereby providing more economical manufacturing, andalso may be removed from the hub cap for servicing.

Optionally, components of first embodiment tire inflation system 70provide a modular design that enables different configurations for thesystem, depending on design and/or use requirements. As shown in FIGS.2-4, hub cap 72 of first embodiment tire inflation system 70 may beconfigured for tire inflation, deflation, and pneumatic balancing byemploying hub cap 72 with dual wheel valve 144 and rotary union 86.

Alternatively, as shown in FIG. 5, first embodiment tire inflationsystem 70 may employ hub cap 72 and rotary union 86 without dual wheelvalve 144 to provide tire inflation without deflation and pneumaticbalancing. More particularly, an outboard cover plate 160 formed with achannel 162 may be mounted to outboard surface 142 of hub cap outboardwall 76. Channel 162 enables air to flow from center port 140 to eachrespective offset port 154A, 154B, through cylindrical bores 112A, 112B,and through tire hoses 118A, 118B to the tires. When cover plate 160 isused, the shape of poppet valve assembly 124 is configured so that itdoes not hold Schrader valve 134 open. As a result, air is able to flowfrom each offset port 154A, 154B through respective tire hoses 118A,118B and into the tires, but is unable to flow back out of the tires.Because air is unable to flow from tires back through outboard coverplate 160 to center port 140 in this configuration, tire inflationsystem 70 provides tire inflation without deflation or balancing.

As an additional alternative, as shown in FIG. 6, first embodiment tireinflation system 70 may employ hub cap 72 and dual wheel valve 144 toenable fluid communication and pneumatic balancing between the tiresindependently of rotary union 86 and pneumatic conduit 96 (FIG. 5). Moreparticularly, an inboard cover plate 164 may be mounted on inboardsurface 82 of hub cap outboard wall 76 over supply cavity 110. Hub cap72 and dual tire valve 144 enable fluid communication between the tiresand enables them to have a generally uniform or balanced inflationpressure. More specifically, first tire hose 118A, first cylindricalbore 112A, first offset port 154A, and first wheel valve 148A fluidlycommunicate with second wheel valve 148B, second offset port 154B,second cylindrical bore 112B, and second tire hose 118B at center port140 along the fluid path provided from each respective wheel valve tothe center port by distribution plate 152. Because supply cavity 110 iscovered by inboard cover plate 164, there is no fluid communication pastsupply cavity 110, so that in this configuration, dual wheel valve 144provides pneumatic balancing between the tires independently ofinflation or deflation.

The modular design of components of first embodiment tire inflationsystem 70 enable a standard or stock heavy-duty vehicle to be easilyconverted between different configurations for the system, such asinflation, deflation and pneumatic balancing; inflation withoutdeflation and pneumatic balancing; and pneumatic balancing independentlyof inflation and deflation. First embodiment tire inflation system 70enables such a conversion to be made quickly and easily using one hubcap 72 and simple outboard and inboard cover plates 160, 164,respectively.

Turning now to FIGS. 7-12B, a second and preferred exemplary embodimentof a constant pressure pneumatic balancing tire inflation system of thepresent invention is indicated generally at 170. Second exemplaryembodiment tire inflation system 170 integrates a wheel valve assembly172, shown by way of example as a dual wheel valve, into an intermediatewall 174 of a hub cap 176, as will be described in greater detail below.Integrating dual wheel valve 172 into hub cap intermediate wall 174protects the wheel valve from environmental impact and environmentalcontamination. It is to be understood that tire inflation system 170includes an air source, such as an air tank (not shown), which is influid communication with the vehicle tires (not shown) via a pneumaticconduit 96 (FIG. 2) and other components, which will be described indetail below. It is also to be understood that means known to thoseskilled in the art, such as mechanically-operated regulator valves (notshown), are fluidly connected to pneumatic conduit 96 and are employedto monitor the pneumatic pressure in the tires and to actuate inflationand/or deflation of the tires.

With particular reference now to FIGS. 7-9 and 12A-12B, hub cap 176 ofsecond exemplary embodiment tire inflation system 170 includes acylindrical side wall 178. Intermediate wall 174 is integrally formedbetween an inboard end of hub cap 176 and an outboard end 200 of sidewall 178, and preferably nearer to the side wall outboard end, andextends generally perpendicular to the side wall. It is to be understoodthat other shapes and configurations of hub cap side wall 178 andintermediate wall 174 may be employed without affecting the overallconcept or operation of the present invention, such as an integrateddome or cone shape formed as one piece or multiple pieces, and/oradjusting the intermediate wall to be an outboard wall. Aradially-extending flange 180 is formed on an inboard end of side wall178, and is formed with a plurality of bolt openings 182 to enable bolts(not shown) to secure hub cap 176 to the outboard end of wheel hub 22(FIG. 1). In this manner, hub cap 176 defines an interior compartment184. It is to be understood that means known to those skilled in the artother than bolts may be used to secure hub cap 176 to wheel hub 22, suchas a threaded connection between the hub cap and wheel hub, other typesof mechanical fasteners, and/or a press fit.

With additional reference to FIG. 10, hub cap 176 also includes adiscrete outboard wall 190 that seats in a circumferentially-extendinggroove 192 formed in side wall outboard end 200. Outboard wall 190extends generally perpendicular to side wall 178, and a fluid seal isprovided between the outboard wall and the hub cap side wall by an innergasket 194, which is disposed between the outboard wall and the base ofgroove 192. Outboard wall 190 is secured in groove 192 by a retainingring 196. An outer gasket 198 is disposed between outboard wall 190 andretaining ring 196 to provide a fluid seal between the outboard wall andthe retaining ring. Retaining ring 196 is formed with openings 202, andbolts or other mechanical fasteners 228 extend through the retainingring openings and aligned ones of openings 197 and 199 formed in outergasket 198 and side wall outboard end 200, respectively, to secure theretaining ring and the outer gasket to the hub cap side wall.Optionally, outboard wall 190 may be transparent or translucent in orderto provide convenient visual inspection of the wheel end lubricant levelwhen an oil-type lubricant is employed. When grease-type lubricant isemployed, outboard wall 190 may be opaque.

A pneumatic distribution plate 204 is disposed between hub capintermediate wall 174 and rotary union 86. More particularly, pneumaticdistribution plate 204 includes an outboard surface 206 (FIG. 12B) thatis disposed against an inboard surface 186 of hub cap intermediate wall174, and an inboard surface 208 (FIG. 12A) that is disposed againstrotary union 86. Preferably, bolts 188 or other mechanical fastenerssecure cylindrical housing 84 of rotary union 86 to pneumaticdistribution plate 204, and also secure the pneumatic distribution plateto inboard surface 186 of hub cap intermediate wall 174. Theconstruction of rotary union 86 is similar to that as described abovefor first embodiment tire inflation system 70, including a stem 90having inboard portion 92 that engages pneumatic conduit 96 (FIG. 2) andoutboard portion 98 that is rotatably mounted in rotary union housing 84via bearings 102.

By way of example, to inflate the vehicle tires, air flows frompneumatic conduit 96 through central bore 100 formed in rotary unionstem 90 to pneumatic distribution plate 204. With particular referenceto FIGS. 8-9 and 12A-12B, pneumatic distribution plate 204 includes acentral recess 210, which enables housing 84 of rotary union 86 to seaton inboard surface 208 of the pneumatic distribution plate. When rotaryunion 86 seats on inboard surface 208 of pneumatic distribution plate204, a supply cavity 212 is formed between the rotary union and thepneumatic distribution plate at central recess 210. A pair of supplyopenings 214 is formed in pneumatic distribution plate 204 at centralrecess 210, which enables air to flow from central bore 100 of rotaryunion stem 90, through supply cavity 212 and into the pneumaticdistribution plate.

With additional reference to FIG. 7, each one of supply openings 214 inpneumatic distribution plate 204 fluidly communicate with a respectivewheel valve 148A, 148B housed in hub cap intermediate wall 174. Moreparticularly, hub cap intermediate wall 174 acts as a dual wheel valvehousing, being formed with respective integral wheel valve housingchambers 216A, 216B. Hub cap intermediate wall 174 enables air to beprovided to two separate tires from a single port, that is, from supplycavity 212, with a wheel valve 148A, 148B mounted in each wheel valvehousing chamber 216A, 216B for each respective tire, without employingexterior pneumatic conduit or hoses. More particularly, air flowsthrough supply cavity 212 and through supply openings 214 in pneumaticdistribution plate 204, which divide the air flow into two separatepaths, so that air flows into each wheel valve 148A, 148B.

Each wheel valve 148A, 148B is similar to that as described above forfirst embodiment tire inflation system 70. More particularly, each wheelvalve 148A, 148B preferably is a diaphragm valve that remains openduring all normal operating conditions and is also capable of isolatingeach tire in tire inflation system 170 from one or more tires thatexperience a significant pressure loss, such as if the tire ispunctured. Each wheel valve 148A, 148B is also capable of isolating eachtire from the other components of tire inflation system 170 if thesystem develops a leak that exceeds the inflation capacity of thesystem. That is, each wheel valve 148A, 148B preferably is spring biasedand actuates or opens at a selected pressure setting or pressure level,which is below or less than the minimum pressure that would be expectedto be utilized as a target tire pressure.

For example, wheel valve 148A, 148B may open or actuate at a reasonablepredetermined pressure level that is lower than the target inflationpressure, such as at about 70 pounds per square inch (psi) when thetarget inflation pressure is at about 90 psi. Alternatively, wheel valve148A, 148B may open or actuate at a pressure level that is a setreasonable amount less than the target inflation pressure, such as avalue of about 20% less than the target inflation pressure, or a valueof about 20-30 psi less than the target inflation pressure. In thismanner, each wheel valve 148A, 148B remains open during all normaloperating conditions, thereby enabling air to flow to the tires, andalso enabling fluid communication between the tires for balancing ofpneumatic pressure, as will be described in greater detail below.

In the event of a significant pressure loss in one of the tires or inthe pneumatic components of tire inflation system 170 that allows thepressure level in pneumatic conduit 96 to fall below the selectedpressure setting, the spring bias of wheel valves 148A, 148B causes themto close, thus isolating each tire from the rest of the tire inflationsystem. For example, if the opening or actuation pressure level of wheelvalve 148A, 148B is 70 psi and the pressure in pneumatic conduit 96drops below 70 psi, each wheel valve closes and thus isolates the tires.Actuation of each wheel valve 148A, 148B at a reasonable pressure levelbelow the target inflation pressure prevents excessive deflation of thetires and thereby provides emergency protection, in contrast to wheelvalves of the prior art. More particularly, prior art wheel valves openat an extremely low pressure level, such as about 10-20 psi. As aresult, in the event that one or more tires experience a significantpressure loss or system 170 develops a leak that exceeds the inflationcapacity of the system, the prior art wheel valves remain open until thesystem pressure drops to 10-20 psi, which in turn allows significantundesirable deflation of the tires.

In addition, each wheel valve 148A, 148B provides means to enableisolation of the tires from the vehicle supply tank by being rapidlyand/or reliably closed when the vehicle is parked for an extended periodof time. As described above, each wheel valve 148A, 148B is able torespond to the engagement of the vehicle parking brake, or to otherconditions that indicate the vehicle has been parked. In this manner, ifthere is a drop in the supply tank pressure while the vehicle is parked,the isolation of the tires that is enabled by wheel valves 148A, 148Bprevents that drop from reducing the tire pressure.

When each wheel valve 148A, 148B is open, air flows from each respectivewheel valve through a respective wheel valve exit port 218A, 218B formedin pneumatic distribution plate 204, through a respective channel 224(FIG. 8) formed in the pneumatic distribution plate, and out of thepneumatic distribution plate through a respective exit port 220A, 220Bformed in the plate. Each exit port 220A, 220B of pneumatic distributionplate 204 is in fluid communication with a respective cylindrical bore222A, 222B formed in hub cap intermediate wall 174.

Cylindrical bores 222A, 222B are similar to cylindrical bores 112A, 112Bthat are described above for first embodiment tire inflation system 70.Preferably, cylindrical bores 222A, 222B are formed approximatelyone-hundred-eighty (180) degrees from one another in hub capintermediate wall 174, which enables optimum configuration for two tireshoses 118A, 118B (FIG. 2), with each hose extending to a respective oneof a pair of tires of a heavy-duty vehicle dual-wheel configuration. Aswith first embodiment tire inflation system 70, a coupling 114 of eachtire hose 118A, 118B secures the direct connection of each respectivetire hose 118A, 118B to hub cap 176.

Reference shall now be made to a first bore 222A and its relatedstructure, components and configuration for the purpose of convenience,with the understanding that such structure, components and configurationalso applies to second bore 222B. Fixed bushing or sleeve 122 isreceived in bore 222A, and tire hose fitting 120 of tire hose 118A seatsin the sleeve. Tire hose 118A also includes Schrader valve 134, whichseats in tire hose fitting 120. Poppet valve assembly 124 is similar tothat as described above for first embodiment tire inflation system 70,preventing excessive venting of air from second embodiment tireinflation system 170 upon the removal of tire hose 118A from hub cap176.

The structure of second embodiment tire inflation system 170 providescontinuous balancing of pneumatic pressure across all of the tires inthe system. More particularly, in a pneumatically balanced system 170,the tires are in fluid communication with one another, and according tothe principles of fluid flow, all of the tires have a generally uniform,or balanced, inflation pressure. When this uniform inflation pressure isabove the target pressure, the means that are employed to monitor thetire pressure enable tire inflation system 170 to decrease the uniformpressure by venting excess air to atmosphere as described above, whichin turn decreases the inflation pressure of all of the tires in thesystem to the target pressure. When this uniform inflation pressure isbelow the target pressure, the means that are employed to monitor thetire pressure enable tire inflation system 170 to increase the uniformpressure by supplying air from a vehicle air tank as described above,which in turn increases the inflation pressure of all of the tires inthe system to the target pressure.

In addition, such fluid communication between all of the tires in tireinflation system 170 enables each pair of tires in a dual-wheelconfiguration to have the same pressure level and thus the same actualdiameter, which reduces or eliminates the chance that one of the tireswill experience scrubbing, which increases the life of the tires.Moreover, the fluid communication between all of the tires in tireinflation system 170 enables tires that are at the target pressure tocontribute air to a tire with an excessively low inflation pressure,reducing the chance that a tire may operate with an excessively lowinflation pressure.

The continuous balancing of pneumatic pressure of first embodiment tireinflation system 170 is provided by the unique manifolding path providedby hub cap 176. More particularly, the manifolding path may beillustrated using inflation of the vehicle tires by way of example.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure is below adesired level, the means actuate inflation of the tires. Duringinflation, air flows from the vehicle supply tank, through pneumaticconduit 96 (FIG. 3A), through central bore 100 of rotary union stem 90and into supply cavity 212. Air then flows from supply cavity 212through supply openings 214 in pneumatic distribution plate 204, whichdivide the air flow into two separate paths. Air from each path flowsthrough each respective wheel valve 148A, 148B, through a respectivewheel valve exit port 218A, 218B in pneumatic distribution plate 204,out of the pneumatic distribution plate through a respective exit port220A, 220B, and into a respective cylindrical bore 222A, 222B formed inhub cap intermediate wall 174. Air then flows through a respectivepoppet valve assembly 124 and check valve assembly 134 in correspondingbore 222A, 222B, and into tire hoses 118A, 118B and respective tires.Under normal operating conditions, this manifolding air path remainsopen in second embodiment tire inflation system 170 to provide aconstant-pressure system that continuously balances pneumatic pressureacross all of the tires in the system during inflation.

More particularly, first tire hose 118A, first cylindrical bore 222A,first exit port 220A, first wheel valve exit port 218A, and first wheelvalve 148A fluidly communicate with second wheel valve 148B, secondwheel valve exit port 218B, second exit port 220B, second cylindricalbore 222B, and second tire hose 118B at supply openings 214 and supplycavity 212 along the fluid path provided from each respective wheelvalve to the supply cavity by hub cap intermediate wall 174 andpneumatic distribution plate 204. This fluid path provides fluidcommunication between each tire in a dual-wheel configuration. Inaddition, the fluid path continues from supply openings 214, throughsupply cavity 212, central bore 100 of rotary union stem 90, and throughpneumatic conduit 96. Pneumatic conduit 96 is fluidly connected to theremainder of the tires in the system, and thus enables fluidcommunication between all of the tires in tire inflation system 170.Such fluid communication between the tires enables them to have agenerally uniform, or balanced, inflation pressure.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure in the tiresis above a desired level, the means actuate deflation of the tires.Typically in deflation, air is removed from the system via pneumaticconduit 96 (FIG. 2) and vented to atmosphere. The manifolding air pathremains open in second embodiment tire inflation system 170 duringdeflation. More specifically, when each tire hose 118A, 118B isconnected to hub cap 176, tire hose fitting 120 in each respectivecylindrical bore 222A, 222B maintains each respective poppet valveassembly 124 in an open position, thereby enabling air to flow from thetires through check valve assembly 134 and the poppet valve assembly.Air then flows through a respective exit port 220A, 220B in pneumaticdistribution plate 204, through a respective wheel valve exit port 218A,218B of the pneumatic distribution plate, and into each respective wheelvalve 148A, 148B.

As described above, each wheel valve 148A, 148B preferably is springbiased and actuates or opens at a selected pressure level, such as about70 psi, which is below the minimum pressure that would be expected to beutilized as a target tire pressure. As long as the pressure in pneumaticconduit 96 is above this selected pressure level, each wheel valve 148A,148B remains open, thereby enabling air to flow through each wheelvalve. Air then flows from each respective wheel valve 148A, 148Bthrough supply openings 214 in pneumatic distribution plate 204, andeach separate air flow stream merges into a single air flow stream insupply cavity 212.

It is at this point that fluid communication between the tires forcontinuous balancing of pneumatic pressure takes place. Moreparticularly, first tire hose 118A, first cylindrical bore 222A, firstexit port 220A, first wheel valve exit port 218A, and first wheel valve148A fluidly communicate with second wheel valve 148B, second wheelvalve exit port 218B, second exit port 220B, second cylindrical bore222B, and second tire hose 118B at supply openings 214 and supply cavity212 along the fluid path provided from each respective wheel valve tothe supply cavity by hub cap intermediate wall 174 and pneumaticdistribution plate 204. This fluid path provides fluid communicationbetween each tire in a dual-wheel configuration. In addition, the fluidpath continues from supply openings 214, through supply cavity 212,central bore 100 of rotary union stem 90, and through pneumatic conduit96 (FIG. 3B). Pneumatic conduit 96 is fluidly connected to the remainderof the tires in the system, and thus enables fluid communication betweenall of the tires in tire inflation system 170. Such fluid communicationbetween the tires enables them to have a generally uniform, or balanced,pressure when system 170 is in a deflation mode.

It is to be understood that the manifolding air path described above forsecond embodiment tire inflation system 170 provides fluid communicationbetween all of the tires in the system during inflation and deflation,and when the system is not engaged in inflation or deflation. As aresult, second embodiment tire inflation system 170 provides aconstant-pressure system that continuously balances pneumatic pressureacross all of the tires in the system.

In this manner, hub cap 176 provides a unique manifolding path thatcontinuously balances pneumatic pressure between all of the tires intire inflation system 170 under normal operating conditions, without anyelectronic components or controllers. In addition, second embodimenttire inflation system 170 compensates for ambient temperature changes,as the fluid communication between the tires provided by hub cap 176enables increases in pneumatic pressure that are attributable toincreases in ambient temperature to be relieved to atmosphere through acontrol valve assembly (not shown), which is fluidly connected topneumatic conduit 96. The fluid communication between the tires providedby hub cap 176 also enables decreases in pneumatic pressure that areattributable to decreases in ambient temperature to be addressed throughthe introduction of air into pneumatic conduit 96, as described above.

Moreover, the unique manifolding path provided by hub cap 176 connectsrotary union 86, dual wheel valve 172, and tire hoses 118A, 118B with nointermediate hoses or conduit. The elimination of intermediate hoses orconduit in turn reduces the cost and complexity of second embodimenttire inflation system 170 when compared to prior art tire inflationsystems 40.

Dual wheel valve 172 of second embodiment tire inflation system 170 alsoprovides emergency protection in the event that a tire in the systemexperiences significant pressure loss, or if the components of thesystem develop a leak that exceeds the inflation capacity of the system.For example, if a specific tire is punctured or a pneumatic conduitruptures, the pressure in pneumatic conduit 96 may drop. When thepneumatic pressure in pneumatic conduit 96 drops, wheel valves 148A,148B detect the pressure drop. As described above, when the pressuredetected by wheel valves 148A, 148B drops below the selected actuationor opening pressure level for the valves, which is below the minimumpressure that would be expected to be utilized as a target tirepressure, the valves close. Once wheel valves 148A, 148B close, air flowto and from respective tire hoses 118A, 118B and thus the respectivetires is terminated, thereby isolating each tire from the remainder oftire inflation system 70.

Each wheel valve 148A, 148B also provides means to reduce the pressureloss in the tires when the vehicle has been parked for an extendedperiod of time. More particularly, each wheel valve 148A, 148B is ableto be rapidly and/or reliably closed when the vehicle is parked, therebyenabling the isolation of the tires from the supply tank.

Dual wheel valve 172 of second embodiment tire inflation system 170includes additional advantages. For example, by incorporating twoseparate wheel valves 148A, 148B into intermediate hub cap wall 174,dual wheel valve 172 is able to supply air to multiple tires from asingle pneumatic supply conduit 96, and is able to balance air betweenthose tires. Dual wheel valve 172 also monitors the pneumatic pressurein separate tires via separate wheel valves 148A, 148B. By beingintegrated into intermediate wall 174 of hub cap 176, dual wheel valve172 eliminates external hoses or conduit, in turn reducing the cost andcomplexity of second embodiment tire inflation system 170 when comparedto prior art tire inflation systems 40.

By being integrated into intermediate wall 174 of hub cap 176, dualwheel valve 172 is inside the hub cap, and thus is protected fromenvironmental impact and environmental contamination. In addition, bybeing inside hub cap 176, dual wheel valve 172 includes a protected ventpath for each wheel valve 148A, 148B, enabling each wheel valve housingchamber 216A, 216B to open directly into hub cap interior compartment184 and vent via vent openings 226 (FIGS. 11A and 11B) through axle 10(FIG. 2), which reduces the introduction of environmental contaminantsinto the wheel valves. Integrating dual wheel valve 172 into hub capintermediate wall 174 also enables each wheel valve 148A, 148B to bedisposed in a tamper-resistant location, thereby preventing unauthorizedadjustment of the wheel valve pressure settings.

Alternatively, as shown in FIGS. 13-14, second embodiment tire inflationsystem 170 may employ hub cap 176 and rotary union 86 without dual wheelvalve 172 to provide tire inflation without deflation and pneumaticbalancing. More particularly, an inflation plate 290 formed with achannel 292 may be used in place of pneumatic distribution plate 204(FIG. 9), and wheel valves 148A, 148B are not included in respectivehousing chambers 216A, 216B. Channel 292 enables air to flow from supplycavity 212 to each respective housing chamber 216A, 216B, throughcylindrical bores 222A, 222B, and through tire hoses 118A, 118B to thetires. In this inflation-only setup, the shape of poppet valve assembly124 is configured so that it does not hold Schrader valve 134 open. As aresult, air is able to flow from each respective housing chamber 216A,216B through respective tire hoses 118A, 118B and into the tires, but isnot able to flow back out of the tires. Because air is not able to flowfrom tires back through inflation plate 290 to supply cavity 212 in thisconfiguration, tire inflation system 170 provides tire inflation withoutdeflation or balancing.

As an additional alternative, as shown in FIGS. 15-16, second embodimenttire inflation system 170 may employ hub cap 176 and a single wheelvalve 148A to enable fluid communication and pneumatic balancing betweenthe tires independently of rotary union 86 and pneumatic conduit 96(FIG. 5). More particularly, an inboard cover plate 294 may be used inplace of pneumatic distribution plate 204 (FIG. 9). Hub cap 176 andwheel valve 148A enable fluid communication between the tires andenables them to have a generally uniform or balanced inflation pressure.More specifically, first tire hose 118A, first cylindrical bore 222A,first exit port 220A, first wheel valve exit port 218A, and first wheelvalve 148A fluidly communicate with second wheel valve exit port 218B,second exit port 220B, second cylindrical bore 222B, and second tirehose 118B at supply openings 214 and supply cavity 212 along the fluidpath provided from each respective wheel valve to the supply cavity byhub cap intermediate wall 174 and inboard cover plate 294. Because thereis no fluid communication inboardly beyond inboard cover plate 294,wheel valve 148A provides pneumatic balancing between the tiresindependently of inflation and deflation.

The modular design of components of second embodiment tire inflationsystem 170 enable a standard or stock heavy-duty vehicle to easilyconvert between different configurations for the system, such asinflation, deflation and pneumatic balancing; inflation withoutdeflation and pneumatic balancing; and pneumatic balancing independentlyof inflation and deflation. Second embodiment tire inflation system 170enables such a conversion to be made quickly and easily using one hubcap 176 and simple inflation plate 290 and inboard cover plate 294,respectively.

Turning now to FIG. 17, a third exemplary embodiment of a constantpressure pneumatic balancing tire inflation system of the presentinvention is indicated generally at 230. Third exemplary embodiment tireinflation system 230 employs a discrete wheel valve assembly 232, shownby way of example as a dual wheel valve, mounted on an inboard surface234 of an outboard wall 236 of a hub cap 238, as will be described ingreater detail below. Mounting dual wheel valve 232 on inboard surface234 of hub cap outboard wall 236 protects the wheel valve fromenvironmental impact and environmental contamination. It is to beunderstood that tire inflation system 230 includes an air source, suchas an air tank (not shown), which is in fluid communication with thevehicle tires (not shown) via a pneumatic conduit 96 and othercomponents, which will be described in detail below. It is also to beunderstood that means known to those skilled in the art, such asmechanically-operated regulator valves (not shown), are fluidlyconnected to pneumatic conduit 96 and are employed to monitor thepneumatic pressure in the tires and to actuate inflation and/ordeflation of the tires.

Hub cap 238 of second exemplary embodiment tire inflation system 230includes a cylindrical side wall 240, and outboard wall 236 isintegrally formed with the outboard end of the side wall and extendsgenerally perpendicular to the side wall. It is to be understood thatother shapes and configurations of hub cap side wall 240 and outboardwall 236 may be employed without affecting the overall concept oroperation of the present invention, such as an integrated dome or coneshape formed as one piece or multiple pieces. A radially-extendingflange 242 is formed on the inboard end of side wall 240, and is formedwith a plurality of bolt openings (not shown) to enable bolts to securehub cap 238 to the outboard end of wheel hub 22 (FIG. 1). In thismanner, hub cap 238 defines an interior compartment 244. It is to beunderstood that means known to those skilled in the art other than boltsmay be used to secure hub cap 238 to wheel hub 22, such as a threadedconnection between the hub cap and wheel hub, other types of mechanicalfasteners, and/or a press fit.

Dual wheel valve 232 is integrated or directly attached to hub cap 238in hub cap interior compartment 244. More particularly, dual wheel valve232 includes an outboard surface 246 that is disposed against inboardsurface 234 of hub cap outboard wall 236, and an inboard surface 248that is disposed against rotary union 86. Preferably, bolts 250 or othermechanical fasteners secure cylindrical housing 84 of rotary union 86 todual wheel valve 232, and also secure the dual wheel valve to inboardsurface 234 of hub cap outboard wall 236. The construction of rotaryunion 86 is similar to that as described above for first embodiment tireinflation system 70, including a stem 90 having inboard portion 92 thatengages pneumatic conduit 96 and outboard portion 98 that is rotatablymounted in rotary union housing 84 via bearings 102.

By way of example, to inflate the vehicle tires, air passes frompneumatic conduit 96 through central bore 100 formed in rotary unionstem 90 to a fluid passage 252 formed in a body 254 of dual wheel valve232. Dual wheel valve 232 includes a distribution plate 256 at wheelvalve outboard surface 246. Air flows through fluid passage 252 in dualwheel valve 232 into a central passage 258 formed in distribution plate256, and the distribution plate divides the air flow into two separatepaths, so that air flows through exit ports 260A, 260B formed in thedistribution plate, and into each respective wheel valve 148A, 148B.

Each wheel valve 148A, 148B is similar to that as described above forfirst embodiment tire inflation system 70. More particularly, each wheelvalve 148A, 148B preferably is a diaphragm valve that remains openduring all normal operating conditions, and is also capable of isolatingeach tire in tire inflation system 230 from one or more tires thatexperience a significant pressure loss, such as if a tire is punctured.Each wheel valve 148A, 148B is also capable of isolating each tire fromthe other components of tire inflation system 230 if the system developsa leak that exceeds the inflation capacity of the system. That is, eachwheel valve 148A, 148B preferably is spring biased and actuates or opensat a selected pressure setting or pressure level, which is below or lessthan the minimum pressure that would be expected to be utilized as atarget tire pressure.

For example, wheel valve 148A, 148B may open or actuate at a reasonablepredetermined pressure level that is lower than the target inflationpressure, such as at about 70 pounds per square inch (psi) when thetarget inflation pressure is at about 90 psi. Alternatively, wheel valve148A, 148B may open or actuate at a pressure level that is a setreasonable amount less than the target inflation pressure, such as avalue of about 20% less than the target inflation pressure, or a valueof about 20-30 psi less than the target inflation pressure. In thismanner, each wheel valve 148A, 148B remains open during all normaloperating conditions, thereby enabling air to flow to the tires, andalso enabling fluid communication between the tires for balancing ofpneumatic pressure, as will be described in greater detail below.

In the event of a significant pressure loss in one of the tires or inthe pneumatic components of tire inflation system 230 that allows thepressure level in pneumatic conduit 96 to fall below the selectedpressure setting, the spring bias of wheel valves 148A, 148B causes themto close, thus isolating each tire from the rest of the tire inflationsystem. For example, if the opening or actuation pressure level of wheelvalve 148A, 148B is 70 psi and the pressure in pneumatic conduit 96drops below 70 psi, each wheel valve closes and thus isolates the tires.Actuation of each wheel valve 148A, 148B at a reasonable pressure levelbelow the target inflation pressure prevents excessive deflation of thetires and thereby provides emergency protection, in contrast to wheelvalves of the prior art. More particularly, prior art wheel valves openat an extremely low pressure level, such as about 10-20 psi. As aresult, in the event that one or more tires experience a significantpressure loss or system 230 develops a leak that exceeds the inflationcapacity of the system, the prior art wheel valves remain open until thesystem pressure drops to 10-20 psi, which in turn allows significantundesirable deflation of the tires.

In addition, each wheel valve 148A, 148B provides means to enable theisolation of the tires from the vehicle supply tank by being able to berapidly and/or reliably closed when the vehicle is parked for anextended period of time. As described above, each wheel valve 148A, 148Bis able to respond to the engagement of the vehicle parking brake, or toother conditions that indicate the vehicle has been parked. In thismanner, if there is a drop in the supply tank pressure while the vehicleis parked, the isolation of the tires that is enabled by wheel valves148A, 148B prevents that drop from reducing the tire pressure.

When each wheel valve 148A, 148B is open, air flows from each respectivewheel valve through a respective wheel valve exit port 262A, 262B, andthrough respective ports 264A, 264B formed in hub cap outboard wall 236to a manifold block 266 that is mounted on outboard surface 246 of thehub cap outboard wall. Manifold block 266 is formed with respectivechannels 268A, 268B (only 268A shown) which fluidly communicate witheach respective port 264A, 264B formed in hub cap outboard wall 236.Channels 268A, 268B formed in manifold block 266, in turn, are fluidlyconnected to each respective tire hose 118A, 118B. Optionally, ports264A, 264B formed in hub cap outboard wall 236 may fluidly communicatewith respective cylindrical bores 112A, 112B formed in manifold block266. Cylindrical bores 112A, 112B are fluidly connected to eachrespective tire hose 118A, 118B, including coupling 114, hose fitting120, and Schrader valve 134 of each tire hose, and associated poppetvalve assemblies 124, as described above for first embodiment tireinflation system 70. Preferably, tire hoses 118A, 118B are configuredaccording to a non-axial tire hose fitting system 270 (FIG. 18), whichis described in greater detail below.

The structure of third embodiment tire inflation system 230 providescontinuous balancing of pneumatic pressure across all of the tires inthe system. More particularly, in a pneumatically balanced system 230,the tires are in fluid communication with one another, and according tothe principles of fluid flow, all of the tires have a generally uniform,or balanced, inflation pressure. When this uniform inflation pressure isabove the target pressure, the means that are employed to monitor thetire pressure enable tire inflation system 230 to decrease the uniformpressure by venting excess air to atmosphere as described above, whichin turn decreases the inflation pressure of all of the tires in thesystem to the target pressure. When this uniform inflation pressure isbelow the target pressure, the means that are employed to monitor thetire pressure enable tire inflation system 230 to increase the uniformpressure by supplying air from a vehicle tank as described above, whichin turn increases the inflation pressure of all of the tires in thesystem to the target pressure.

In addition, such fluid communication between all of the tires in tireinflation system 230 enables each pair of tires in a dual-wheelconfiguration to have the same pressure level and thus the same actualdiameter, which reduces or eliminates the chance that one of the tireswill experience scrubbing, which increases the life of the tires.Moreover, the fluid communication between all of the tires in tireinflation system 230 enables tires that are at the target pressure tocontribute air to a tire with an excessively low inflation pressure,reducing the chance that a tire may operate with an excessively lowinflation pressure.

The continuous balancing of pneumatic pressure of third embodiment tireinflation system 230 is provided by the unique manifolding path of hubcap 238 and dual wheel valve 232. More particularly, the manifoldingpath may be illustrated using inflation of the vehicle tires by way ofexample.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure in the tiresis below a desired level, the means actuate inflation of the tires.During inflation, air flows from the vehicle supply tank, throughpneumatic conduit 96, through central bore 100 of rotary union stem 90and into fluid passage 252 in dual wheel valve 232. Air flows throughdual wheel valve fluid passage 252 and through central passage 258 indistribution plate 256, which divides the air flow into two separatepaths. Air from each path flows through distribution plate exit ports260A, 260B, and into each respective wheel valve 148A, 148B. When eachwheel valve 148A, 148B is open, air flows from each respective wheelvalve through respective wheel valve exit ports 262A, 262B and throughrespective ports 264A, 264B formed in hub cap outboard wall 236 tochannels 268A, 268B in manifold block 266, and into tire hoses 118A,118B and respective tires. Under normal operating conditions, thismanifolding air path remains open in third embodiment tire inflationsystem 230 to provide a constant-pressure system that continuouslybalances pneumatic pressure across all of the tires in the system duringinflation.

More particularly, first tire hose 118A, first manifold block channel268A, first hub cap outboard wall port 264A, first wheel valve exit port262A, and first wheel valve 148A fluidly communicate with second wheelvalve 148B, second wheel valve exit port 262B, second hub cap outboardwall port 264B, second manifold block channel 268B, and second tire hose118B at the distribution plate central passage. This fluid path providesfluid communication between each tire in a dual-wheel configuration. Inaddition, the fluid path continues through fluid passage 252 in dualwheel valve 232, central bore 100 of rotary union stem 90, and throughpneumatic conduit 96. Pneumatic conduit 96 is fluidly connected to theremainder of the tires in the system, and thus enables fluidcommunication between all of the tires in tire inflation system 230.Such fluid communication between the tires enables them to have agenerally uniform, or balanced, inflation pressure.

When the means that are employed to monitor the pneumatic pressure inthe tires, as described above, determine that the pressure in the tiresis above a desired level, the means actuate deflation of the tires.Typically in deflation, air is removed from the system via pneumaticconduit 96 and vented to atmosphere. The manifolding air path remainsopen in third embodiment tire inflation system 230 during deflation.More specifically, when each tire hose 118A, 118B is connected to hubcap 238, air flows from the tires through manifold block 266, throughchannels 268A, 268B in the manifold block, through respective ports264A, 264B formed in hub cap outboard wall 236, through wheel valve exitports 262A, 262B in distribution plate 256 and into each respectivewheel valve 148A, 148B.

As described above, each wheel valve 148A, 148B preferably is springbiased and actuates or opens at a selected pressure level that is belowthe minimum pressure that would be expected to be utilized as a targettire pressure. As long as the pressure in pneumatic conduit 96 is abovethis selected pressure level, each wheel valve 148A, 148B remains open,thereby enabling air to flow through each wheel valve. Air then flowsfrom each respective wheel valve 148A, 148B through distribution plateexit ports 260A, 260B, and through distribution plate 256 todistribution plate central passage 258.

It is at this point that fluid communication between the tires forcontinuous balancing of pneumatic pressure takes place. Moreparticularly, first tire hose 118A, first manifold block channel 268A,first hub cap outboard wall port 264A, first wheel valve exit port 262A,and first wheel valve 148A fluidly communicate with second wheel valve148B, second wheel valve exit port 262B, second hub cap outboard wallport 264B, second manifold block channel 268B, and second tire hose 118Bat the distribution plate central passage. This fluid path providesfluid communication between each tire in a dual-wheel configuration. Inaddition, the fluid path continues through fluid passage 252 in dualwheel valve 232, central bore 100 of rotary union stem 90, and throughpneumatic conduit 96. Pneumatic conduit 96 is fluidly connected to theremainder of the tires in the system, and thus enables fluidcommunication between all of the tires in tire inflation system 230.Such fluid communication between the tires enables them to have agenerally uniform, or balanced, pressure when system 230 is in adeflation mode.

It is to be understood that the manifolding air path described above forthird embodiment tire inflation system 230 provides fluid communicationbetween all of the tires in the system during inflation and deflation,and when the system is not engaged in inflation or deflation. As aresult, third embodiment tire inflation system 230 provides aconstant-pressure system that continuously balances pneumatic pressureacross all of the tires in the system.

In this manner, hub cap 238 provides a unique manifolding path thatcontinuously balances pneumatic pressure between all of the tires intire inflation system 230 under normal operating conditions, without anyelectronic components or controllers. In addition, third embodiment tireinflation system 230 compensates for ambient temperature changes, as thefluid communication between the tires provided by hub cap 238 enablesincreases in pneumatic pressure that are attributable to changes inambient temperature to be relieved to atmosphere through a control valveassembly (not shown), which is fluidly connected to pneumatic conduit96. The fluid communication between the tires provided by hub cap 238also enables decreases in pneumatic pressure that are attributable todecreases in ambient temperature to be addressed through theintroduction of air into pneumatic conduit 96, as described above.

Moreover, the unique manifolding path provided by hub cap 238 connectsrotary union 86, dual wheel valve 232, and tire hoses 118A, 118B with nointermediate hoses or conduit. The elimination of intermediate hoses orconduit in turn reduces the cost and complexity of third embodiment tireinflation system 230 when compared to prior art tire inflation systems40.

Dual wheel valve 232 of third embodiment tire inflation system 230 alsoprovides emergency protection in the event a tire in the systemexperiences significant pressure loss, or if the components of thesystem develop a leak that exceeds the inflation capacity of the system.For example, if a specific tire is punctured or a pneumatic conduitruptures, the pressure in pneumatic conduit 96 may drop. When thepneumatic pressure in pneumatic conduit 96 drops, the wheel valves 148A,148B detect the pressure drop. As described above, when the pressuredetected by wheel valves 148A, 148B drops below the selected actuationor opening pressure level for the valves, which is below the minimumpressure that would be expected to be utilized as a target tirepressure, the valves close. Once wheel valves 148A, 148B close, air flowto and from respective tire hoses 118A, 118B and thus the respectivetires is terminated, thereby isolating each tire from the remainder oftire inflation system 230.

Each wheel valve 148A, 148B also provides means to reduce the pressureloss in the tires when the vehicle has been parked for an extendedperiod of time. More particularly, each wheel valve 148A, 148B is ableto be rapidly and/or reliably closed when the vehicle is parked, therebyenabling isolation of the tires from the supply tank.

Dual wheel valve 232 of third embodiment tire inflation system 230includes additional advantages. For example, by incorporating twoseparate wheel valves 148A, 148B into a single valve body 254, dualwheel valve 232 is able to supply air to multiple tires from a singlepneumatic supply conduit 96, and in cooperation with hub cap 238, isable to balance air between those tires. Dual wheel valve 232 provides aconvenient, compact unit, while also being able to monitor the pneumaticpressure in separate tires via separate wheel valves 148A, 148B. Bybeing mounted directly to hub cap 238, dual wheel valve 232 eliminatesexternal hoses or conduit, in turn reducing the cost and complexity ofthird embodiment tire inflation system 230 when compared to prior arttire inflation systems 40. In addition, by being a discrete unit, dualwheel valve 232 may be built or constructed separately from hub cap 238and later mounted on the hub cap, thereby providing more economicalmanufacturing.

By being mounted in hub cap interior compartment 244, dual wheel valve232 is protected from environmental impact and environmentalcontamination. In addition, by being inside hub cap 238, dual wheelvalve 232 includes a protected vent path for each wheel valve 148A,148B, enabling each wheel valve housing chamber to open directly intohub cap interior compartment 244 and vent through axle 10, which reducesthe introduction of environmental contaminants into the wheel valves.Mounting dual wheel valve 232 in hub cap interior compartment 244 alsoenables each wheel valve 148A, 148B to be disposed in a tamper-resistantlocation, thereby preventing unauthorized adjustment of the wheel valvepressure settings.

Turning now to FIG. 18, an optional feature for use with first, secondand third embodiment tire inflation systems 70, 170, 230, respectively,is shown. More particularly, a non-axial tire hose fitting system isindicated generally at 270. Non-axial tire hose fitting system 270includes hose fittings 272A, 272B which are mounted either on anoutboard surface 274 of an outboard wall 276 of a hub cap 278, or on amanifold block 266 (FIG. 17), which in turn is mounted to the hub capoutboard wall, or to a hub cap intermediate wall 174 (FIG. 7). Hosefittings 272A, 272B are located generally non-axially or side-by-side,rather than end-to-end along the same axis, to reduce the overall sizeof system 270. Locating hose fittings 272A, 272B generally side-by-sideis useful when limited space is available on hub cap 278 due to othercomponents that are mounted on the hub cap. In addition, by providing areduced size, non-axial tire hose fitting system 270 desirably enableshub cap 278 to be of a more compact and smaller design than prior arthub cap 24 (FIG. 1).

In this manner, tire inflation system 70, 170, 230 of the presentinvention provides a tire inflation system that is apneumatically-controlled, constant-pressure system which is capable ofdeflation, continuously balances pneumatic pressure across all of thetires in the system, and provides emergency protection in the event thatone or more tires in the system experiences significant pressure loss.More particularly, tire inflation system 70, 170, 230 preferablyincludes hub cap 72, 176, 238, respectively, which acts as a manifoldand cooperates with a wheel valve assembly 144, 172, 232, respectively,each shown by way of example as a dual wheel valve, that is integratedinto or attached to each respective hub cap. Dual wheel valve 144, 172,232 of tire inflation system 70, 170, 230, respectively, includes aconstruction that enables control of pneumatic pressure of a dual-wheelconfiguration of a heavy-duty vehicle. Tire inflation system 70, 170,230 also optionally includes non-axial tire hose fitting 270.

Tire inflation system of the present invention 70, 170, 230 preferablyemploys mechanical components that are mechanically and/or pneumaticallyactuated, rather than electronically-operated solenoid valves,electronic controllers, and other electronic components, which areexpensive and often complex to install and configure. As a result, tireinflation system 70, 170, 230 is simple, economical and easy to install.In addition, by being a mechanically and pneumatically actuated system,tire inflation system of the present invention 70, 170, 230 is reliable,since it does not require the use of the electrical system of thetrailer, which may be unreliable or even non-functional at times.

Moreover, by not exhausting when inflation of the tires is complete,tire inflation system of the present invention 70, 170, 230 is aconstant-pressure system. Such a constant-pressure system 70, 170, 230does not require expensive and complex electronic controls to determinewhen it is necessary to trigger or commence inflation, instead employingmechanical components that are mechanically and/or pneumaticallyactuated. For this additional reason, tire inflation system 70, 170, 230is simple, economical and easy to install, and by not employingelectrical components, does not require the use of the electrical systemof the trailer and thus is relatively reliable. In addition, as aconstant-pressure system, tire inflation system 70, 170, 230 remainscontinuously charged with air, which enables the system to continuouslymonitor tire pressure and dynamically respond to pressure changes, andthereby actively or quickly respond to reduced tire pressure conditions,such as in the case of an air leak, and to increased tire pressureconditions, such as an increase in ambient temperature.

Tire inflation system of the present invention 70, 170, 230 providescontinuous balancing of pneumatic pressure across all of the tires inthe system. Because the structure of tire inflation system 70, 170, 230enables the tires to be in fluid communication with one another, all ofthe tires have a generally uniform, or balanced, inflation pressure.Such fluid communication between all of the tires in tire inflationsystem 70, 170, 230 enables each pair of tires in a dual-wheelconfiguration to have the same pressure level and thus the same actualdiameter, which reduces or eliminates the chance that one of the tireswill experience scrubbing, which increases the life of the tires.Moreover, the fluid communication between all of the tires in tireinflation system 70, 170, 230 enables tires that are at the targetpressure to contribute air to a tire with an excessively low inflationpressure, reducing the chance that a tire may operate with anexcessively low inflation pressure.

Tire inflation system of the present invention 70, 170, 230 alsoprovides emergency protection of the tires in the event that one tireexperiences a significant pressure loss. Thus, if a tire is punctured orthe components of the system develop a leak that exceeds the inflationcapacity of the system, tire inflation system 70, 170, 230 isolates eachtire from the rest of the system, thereby avoiding a significantdecrease of the uniform inflation pressure of all of the tires. Tireinflation system 70, 170, 230 also provides means to reduce the pressureloss in the tires when the vehicle has been parked for an extendedperiod of time by enabling isolation of the tires from the supply tank.

The present invention also includes a method of continuously balancingthe pneumatic pressure across all of the tires in a constant pressuretire inflation system, and a method of providing emergency protection inthe event a tire in the system experiences significant pressure loss.Each method includes steps in accordance with the description that ispresented above and shown in FIGS. 2-18.

It is to be understood that the structure of the above-describedconstant pressure pneumatic balancing tire inflation system may bealtered or rearranged, or certain components omitted or added, withoutaffecting the overall concept or operation of the invention. Forexample, wheel valves 148A, 148B may be piston-style wheel valves,rather than the above-described diaphragm valves. In addition, othershapes and configurations of the walls of hub cap 72, 176, 238, such asan integrated dome or cone shape formed as one piece or multiple pieces,may be employed without affecting the overall concept or operation ofthe invention. Moreover, tire inflation system 70, 170, 230 may employwheel valves 148A, 148B that are not mounted on or connected to a hubcap without affecting the overall concept or operation of the invention.

It is to be further understood that the present invention findsapplication in types of tire inflation systems for heavy-duty vehiclesother than those shown and described herein and which are known to thoseskilled in the art, without affecting the concept or operation of theinvention. Moreover, reference herein has been made to a constantpressure tire inflation system, and such reference includes all tireinflation systems with regulated pressure. For example, constantpressure systems include systems in which all or a significant portionof the pneumatic conduit of the system remains pressurized or chargedwith compressed air when the system is not engaged in inflation ordeflation, and systems in which such pressurization of the pneumaticconduit may be interrupted by a switch or other component. Moreover,gases other than air that may be compressed and follow the principles offluid flow, including nitrogen, carbon dioxide, and the like, may beemployed without affecting the concept or operation of the invention.

While reference herein has been made generally to a heavy-duty vehiclefor the purpose of convenience, it has been with the understanding thatsuch reference includes trucks, tractor-trailers and semi-trailers, andtrailers thereof. In addition, while axle 10 has been shown by way ofexample as a non-drive axle, the present invention applies to all typesof axles known in the art, including drive axles and non-drive axles.

Accordingly, the improved constant pressure pneumatic balancing tireinflation system is simplified, provides an effective, safe,inexpensive, and efficient structure which achieves all the enumeratedobjectives, provides for eliminating difficulties encountered with priorart tire inflation systems, and solves problems and obtains new resultsin the art.

In the foregoing description, certain terms have been used for brevity,clarity and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued. Moreover, the present invention has been described withreference to exemplary embodiments. It shall be understood that thisillustration is by way of example and not by way of limitation, as thescope of the invention is not limited to the exact details shown ordescribed. Potential modifications and alterations will occur to othersupon a reading and understanding of this disclosure, and it isunderstood that the invention includes all such modifications andalterations and equivalents thereof.

Having now described the features, discoveries and principles of theinvention, the manner in which the improved constant pressure pneumaticbalancing tire inflation system is constructed, arranged and used, thecharacteristics of the construction and arrangement, and theadvantageous, new and useful results obtained; the new and usefulstructures, devices, elements, arrangements, parts and combinations areset forth in the appended claims.

What is claimed is:
 1. A constant pressure vehicle tire equalization system, comprising: a hub cap; a first tire fluidly connected to said hub cap; a second tire fluidly connected to said hub cap; and at least one wheel valve mounted in said hub cap and being fluidly connected to said first and second tires, whereby said wheel valve selectively maintains fluid communication and flow between the first and second tires to provide pneumatic balancing between said first and second tires.
 2. The constant pressure vehicle tire equalization system of claim 1, wherein said at least one wheel valve is independent of a vehicle air supply source.
 3. The constant pressure vehicle tire equalization system of claim 1, wherein said at least one wheel valve includes a pair of wheel valves.
 4. The constant pressure vehicle tire equalization system of claim 1, wherein said at least one wheel valve is biased to close when a pressure in at least one of said first and second tires decreases below a predetermined level.
 5. The constant pressure vehicle tire equalization system of claim 1, wherein said system does not employ electronic components.
 6. The constant pressure vehicle tire equalization system of claim 1, wherein said hub cap includes: a generally cylindrical sidewall; an outboard wall extending generally perpendicular to said sidewall at a first end of said hub cap; and a flange extending radially outwardly from said sidewall at a second end of said hub cap.
 7. The constant pressure vehicle tire equalization system of claim 6, wherein said at least one wheel valve is attached to an outboard surface of said outboard wall of said hub cap.
 8. The constant pressure vehicle tire equalization system of claim 6, wherein said at least one wheel valve is attached to an inboard surface of said outboard wall of said hub cap.
 9. The constant pressure vehicle tire equalization system of claim 6, wherein said at least one wheel valve is integrated into said outboard wall of said hub cap.
 10. The constant pressure vehicle tire equalization system of claim 6, wherein said hub cap further comprises an intermediate wall disposed between said outboard wall and said flange.
 11. The constant pressure vehicle tire equalization system of claim 10, wherein said at least one wheel valve is attached to an outboard surface of said intermediate wall of said hub cap.
 12. The constant pressure vehicle tire equalization system of claim 10, wherein said at least one wheel valve is attached to an inboard surface of said intermediate wall of said hub cap.
 13. The constant pressure vehicle tire equalization system of claim 10, wherein said at least one wheel valve is integrated into said intermediate wall of said hub cap.
 14. The constant pressure vehicle tire equalization system of claim 6, wherein said at least one wheel valve is removable from said hub cap.
 15. The constant pressure vehicle tire equalization system of claim 6, wherein said hub cap includes a first port to receive a tire hose of said first tire and a second port to receive a tire hose of said second tire.
 16. The constant pressure vehicle tire equalization system of claim 15, further comprising a first poppet valve assembly disposed in said first port and a second poppet valve assembly disposed in said second port, whereby said poppet valve assemblies enable selective fluid communication between said wheel valves and said tire hoses.
 17. The constant pressure vehicle tire equalization system of claim 6, further comprising a first fitting attached to said hub cap for receiving a tire hose of said first tire and a second fitting attached to the hub cap for receiving a tire hose of said second tire, wherein said first fitting and said second fitting are disposed non-axially on said hub cap.
 18. The constant pressure vehicle tire equalization system of claim 1, wherein said at least one wheel valve includes more than one wheel valve, and said wheel valves are incorporated into a single wheel valve assembly. 